CCSDS标准的建立和演变

Posted on 2022-06-23 Edited on 2022-06-24 In Communications , Deep Space Changyan: Symbols count in article: 22k Reading time ≈ 20 mins.

CCSDS， Consultative Committee for Space Data Systems，空间数据系统咨询委员会，是主要航天国家组成的一个国际技术论坛组织。其在空间数据系统领域上的地位犹如3GPP在移动通信领域的低位，是国际标准事实上的制定者。

主要参考：

张和平等著《空间数据系统》的第2.2节

CCSDS官方网站

计算机网络和移动通信技术的发展和标准化

计算机网络： 创造巨大社会价值

1996年，DARPA 建立 ARPANET：网络功能分层实现；
1983年，ISO 制定 OSI-RM（开放互联参考模型）：七层协议；
1990年代，ARPANET 演变为 INTERNET：TCP/IP 事实标准。

移动通信技术： 技术标准化的典范

1970年代，1G：模拟蜂窝系统（FDMA）；
1980年代，2G：数字蜂窝系统（TDMA（GSM），CDMA（IS-95））；
2000年代，3G：无线宽带数据传输（WCDMA，CDMA2000，TDSCDMA）；
2010年代，4G：正交频分复用（OFDM + MIMO，100Mbps）；
当前，5G 全面开启应用（三大场景：eMBB，uRLLC，MMTC），6G 研发和标准化进行中。

计算机网络和移动通信技术的发展和技术标准的建立为空间数据系统的发展提供了技术上的支撑和实现的可行性。

空间技术发展的需求

空间任务的高投入高风险：

单件研制模式，难以批量制造（任务性质决定）；
各国空间组织独建地面系统，负担沉重（要飞行轨道全覆盖）；

需求牵引：

建立统一的空间数据系统标准，使航天器数据系统资源可重复使用、由设备研制厂商提供可靠、经济的软硬件设备，使空间组织在空间任务中加强合作、共享投资巨大的地面基础设施。

CCSDS的建立和早期工作

1982年10月，CCSDS成立，4个工作组（Panel），其中Panel 1 负责空间通信，即遥测、跟踪和遥控（TT&C，中文统称之的测控）。

Panel 1 从分包遥测和遥测信道编码开始，陆续开发了无线电频率和调制、分包遥控、时间码格式等标准建议书，这些被称为常规在轨系统（Conventional Orbiting System，COS）。1980年达末，完成高级在轨系统（Advanced Orbiting System，AOS）标准建议书系列，以8种业务处理多种信源（数据、语音、图像等）的数据，最终称为国际空间站项目的数据通信标准。

1991年，CCSDS与ISO达成合作协议，在ISO第20技术委员会（航空与航天器）下设立第13分委员会（空间数据和信息传输系统），即 ISO TC20/SC13，负责将 CCSDS 推荐标准按照 ISO 的标准审查和批准程序转化为 ISO 标准。TC20/SC13 实际上主要由 CMC 的成员组成。【一套班子，挂两个牌子。】

CCSDS标准的重规划和新发展

CCSDS当前组织架构

21世纪后，航天任务需求侧的显著变化：

空间数据系统网络化；
深空探测任务显著增加；
- 2022年2月25日，国家航天局、安徽省人民政府、中国科学技术大学共同举行深空探测实验室（天都实验室）揭牌仪式；支持实验室承担探月工程四期（月球科研站）、行星探测工程研制建设任务，牵头论证和实施国际月球科研站、小行星防御系统等重大工程项目。
- 中科大视频：深空科学技术研究院（2022），中科大为对接天都实验室而建。
上行信道更高的速率要求。

2003 年 CCSDS 对其组织结构进行了重新规划设计（Re-Engineered）,借鉴因特网工程任务组（IETF）采用的模式。

CMC 加强了与外界的联系

CMC，即CCSDS管理委员会。

联络员组织（Liaisons）：与空间数据、信息系统相关的政府或私人开发项目的机构；

Liaison organizations are governmental or private activities with developmental programs in the areas of space-related data and information systems. Liaison participation in the working groups is encouraged but not required. When Liaison participation occurs, it usually will be focused on a particular subject of interest to the Liaison organization as opposed to standing involvement, which is not precluded. 当前（2022-6-22）13 个机构主要为美、欧和 ISO 相关机构，无中国机构参与。
协会组织 | 业界关系（Associates | Industrial Relations）：与 CCSDS 保持正是联系以观察和影响 CCSDS 文件开发过程的科学界和工业界实体；

CCSDS Associates are scientific and industrial entities desiring a formal tie with the CCSDS, which allows them to more closely monitor and possibly influence the technical document development process.

Associates may participate in the working groups and in the document development process with the explicit approval of a sponsoring CCSDS Member or Observer Agency. Associates may also submit concept or position papers through their sponsoring Member or Observer Agency. Generally, the sponsor agency and CCSDS Commercial Associate shall be from the same country; however, multinational organizations (e.g., ESA) can sponsor a Associate provided that the Associate candidate is from a country affiliated with the sponsor agency.

当前（2022-6-22）130 个协会组织实体中，只列有一家来自中国的不知名小公司：北京东方飞扬软件技术有限公司 | Beijing Easoaring Software Technology Co., LTD，2017 年7月仅上市半年后即被新三板退市。
客户关系（Customer Relations）：

The Customer Relations function acts as a source of advice and guidance to customers concerning architectural, procedural, and (where appropriate) policy matters pertaining to international space mission cross support and its enabling technologies. It focuses on two-way information exchange, explaining existing CCSDS capabilities to potential customers and sponsors and gathering requirements from them for expanding the suite of CCSDS standards to meet their needs. Customer inputs that are gathered via this function are translated into a proposed work item and often cause a BOF to be initiated. The BOF develops the work proposal and resource estimates so that customer deliverables can be negotiated and resources can be lined up to support the necessary development. Throughout the development process, this function provides the formal interface between the developer and the customer, so that customer satisfaction can be both measured and assured.

CMC 之下还设置了：

空间编号登记机构（Space Assigned Numbers Authority, SANA），负责分配、等级和维护空间协议规定使用的各种编号，例如空间链路协议中用于区分航天器的标识（Spacecraft ID）。

Spacecraft Identifier: https://sanaregistry.org/r/spacecraftid/

天问一号的航天器标识为：2020-049A

扩展阅读：1) 卫星百科-天问一号；2) NASA-Tianwen 1。

CCSDS 工程指导组（CESG）

新组织结构中技术实体为 CCSDS 工程指导组（CESG），其工作划分为 6 大领域：

系统工程领域（System Engineering Area, SEA）：
The SEA supports the work of the CCSDS by providing
- Overall architecture for space mission communications, operations, and cross-support
- Coordination and collaboration with the other areas about architectural choices and options
- Supporting the CESG in evaluating consistency of all area programs of work with the defined architecture
- Creating such working groups and BoFs as are required to progress the work of CCSDS
航天器接口业务领域（Spacecraft Onboard Interface Services Area, SOIS）：

The primary objective of the CCSDS SOIS standard development activities is to radically improve the spacecraft flight segment data systems design and development process by defining generic services that will simplify the way flight software interacts with flight hardware and permitting interoperability and reusability both for the benefit of Agencies and Industrial contractors.

注：该领域副主席（Deputy Area Director）为中国空间技术研究院（CAST，即航天五院）总体部的何熊文（Xiongwen He）。
空间链路业务领域（Space Link Services, SLS）：

The Space Link services area is in charge to develop efficient space link communications systems common to all participating agencies. A space link interconnects a spacecraft with its ground support system or with another spacecraft. Agencies' new generations of space missions require telecommand and telemetry capabilities beyond current technologies. These new needs are for higher data rates, better link performances, more performing ranging systems 【更高数据率、更好服务质量、更有效的测距系统】, together with lower cost, mass and power and higher security 【更低的成本、重量、功耗和更高安全性】.

More specifically, SLS area concentrates on layers 1 & 2 (of OSI protocol stack), namely : RF & modulation, channel coding and data link layer, for both long-haul (e.g.: spacecraft to ground) and proximity links (e.g.: orbiter to lander). Two additional functions are also covered by the SLS area : data compression for end to end data transfer optimization, and ranging for accurate orbit determination.

The area is composed of specialized working group whose objective is to develop specific recommendations. One recommendation will typically cover one OSI layer or sub-layer. This layering of recommendations maximizes flexibility and interoperability with other commercial protocols (e.g. : TCP/IP).
空间链路互联业务领域（Space Internetworking Services, SIS）：

The objective of the Space Internetworking Services (SIS) Area is to address the communications services and protocols supporting end-to-end communications among applications, particularly where those communications may span multiple heterogeneous physical and data link technologies. Areas addressed by SIS include the networking infrastructure to support application-to-application communication onboard a single spacecraft, communications among multiple spacecraft, and communications between space-based applications and their counterparts on Earth and/or other planetary bodies.

The SIS Area deals with communication services and protocols that are independent of specific link technology (as a lower layer bound) and independent of application-specific semantics (as an upper bound). Thus the SIS area covers essentially the network through application layers of the OSI reference model.

SIS protocols use the underlying communication and infrastructure services provided by the Space Link Services (SLS) and Spacecraft Onboard Interface Services (SOIS) areas and any other onboard networks, and provide the networked connectivity needed by applications developed in other CCSDS areas such as Mission Operations and Information Management Services (MOIMS) and Spacecraft Onboard Interface Services (SOIS). The SIS services provide hardware-independent mechanisms for identifying end systems, and provide communications services that allow users to disregard whether the communication is over a single data link layer or over multiple hops. The suite of capabilities developed by the SIS Area accommodates all ranges of delay, interactivity, and directionality, although not all protocols are appropriate for all environments.

The services provided by SIS protocols free applications from having to have intimate knowledge of the underlying communications protocols and mechanisms, and from having to know the physical location(s) of the entities with which they are communicating. This enables applications to focus on the application-specific protocols and interactions necessary to achieve their goals.
任务操作和信息管理业务邻域（Mission Operations and Information Management Services, MOIMS）：

The objective of the Mission Operations and Information Management Services (MOIMS) Area is to address all of the flight execution phase applications that are required to operate the spacecraft and its ground system in response to mission objectives, and their associated detailed information management standards and processes. The focus of this Area is primarily on the “mission operations” functions that occur on a timescale driven by the flight path of the space vehicle. In many cases a dedicated community conducts these mission operations, while “mission utilization” occurs on a timescale that is convenient for users and is often conducted by a separate community. The MOIMS Area ensures that application standards exist which facilitate the smooth transition of space mission information between the “mission operations” systems and the “mission utilization” systems.
交互支持业务领域（Cross Support Services, CSS）：

The Cross Support Services (CSS) Area addresses how space network resources are made available by one organization to another for the purpose of "Cross Support". The objective of the CSS Area is therefore to define what services are required at various cross-support interface points, and how those services are exposed, scheduled and used by organizations that want to confederate their infrastructure in order to execute a mission.

每个业务领域根据工作内容，设置和管理若干工作组（WG）和筹备组（BOF, Birds of a feather）。

BOF：由持相同理念和兴趣的专家组成的筹备组，开展概念研究等准备工作，待条件成熟后转为 WG。

分领域的工作组

2022-6-23 https://cwe.ccsds.org/default.aspx

系统工程（SEA）：
1. 系统体系架构（Systems Architecture）WG：
  
  every standard is consistent and coherent with any other standard, a reference architecture that can be used as a common framework by all the Working Groups and also by engineers in the member Agencies to build systems and to provide services.
2. 安全（Security）WG
3. Delta-DOR WG：
  
  developing an integrated approach for delta differential one way ranging (D-DOR) end to end services. （Coordinate work in other WGs (SIS/Ranging, CSS/CSTS, MOIMS/Nav)）
4. 时间管理（Time Management）WG：
  
  creating and maintaining standards relating to time transfer, time correlation, and time synchronization in space operations contexts.
任务操作和信息管理业务（MOIMS）：
1. 数据存档互操作（Data Archive Interoperability）WG
2. 导航（Navigation）WG
3. 航天器检测和控制（Spacecraft Monitor and Control）WG
4. 任务规划和调度（Mission Planning & Scheduling）WG
交互支持业务（CSS）：
1. 业务管理（Service Management）WG：
  
  The use of Space Link Extension services require the exchange of information that will allow a space flight mission to acquire those services from SLE service providers.
2. 传送业务（Transfer Services）WG：
  
  The Applications Support Services Working Group defines standard services that are provided to onboard software applications. These services isolate the flight software from the underlying hardware details and thereby increase the portability and reuse potential of the flight software. Furthermore, the service access points constitute cross support interfaces.
航天器接口业务（SOIS）
1. 应用支持业务（Application Support Services）WG：
  
  The Applications Support Services Working Group defines standard services that are provided to onboard software applications. These services isolate the flight software from the underlying hardware details and thereby increase the portability and reuse potential of the flight software. Furthermore, the service access points constitute cross support interfaces.
2. 星载无线接口（Onboard Wireless）WG：
  The short term aims will be
  - Identify scenarios in future missions where the use of wireless interfaces are of interest and offer advantages.
  - Document the experiences and best current practices in developing wireless interfaces for spacecraft.
  - Based on lessons learned and experience in implementing wireless interfaces (optical and RF) in past and current space projects, identify the key issues that need to be addressed when implementing wireless interfaces for future spacecraft.
  - Examine existing activities in the SOIS area and in CCSDS to see which of these issues are already being addressed, and which still need to be addressed.
  - Examine the areas that are not currently being addressed, and if necessary generate a proposal for new work items to address them.
3. 亚网层业务（Subnetwork Services）WG： > The Subnetwork Services Working Group is concerned with the transfer of information onboard a spacecraft between its constituent subsystem components. In practice this involves both hardwired systems and wireless systems.
空间链路业务（SLS）：
1. 射频调制（RF Modulation）WG
2. 空间链路编码/同步（Space Link Coding and Synchronization）WG：
  
  The wide range of environment (space-Earth or space-space, near Earth congested bands and deep space link operations in extreme conditions of SNR, links dependent of atmospheric conditions in the new high frequency bands, optical links) requires coding systems with different levels of power efficiency and bandwidth efficiency, or different levels of link reliability or delivered data quality; This work will concentrate on updating the existing set of Channel Coding Blue Books to incorporate recommended coding scheme for new bandwidth efficient codes with low complexity. The update work includes also the extraction of the coding layer out of CCSDS 211.0-B Prox-1 Protocol.
3. 数据压缩（Data Compression）WG
4. 空间链路协议（Space Link Protocols）WG：
  
  This WG develops and adapts wherever possible link layer protocols for new mission environments (proximity communication, formation flying, optical communication, missions utilizing high rate telemetry and telecommand.
5. 空间数据链路安全（Space Data Link Layer Security）WG：
  
  The objectives of this Working Group is to develop a recommendation for a security protocol operating at the data link layer of CCSDS spacelinks. Target missions are civilian missions (science, earth observation, telecommunications, ...). This security protocol should provide authentication and/or encryption both for uplink and downlink. It should be compatible with CCSDS TM, TC and AOS data link protocols and be independent from any specific cryptographic algorithm.
6. 光通信（Optical Communications）WG
空间网络互联（SIS）：
1. 运动图像和应用（Motion Imagery and Application）WG
2. 容延迟网络（Delay Tolerant Networking）WG：
  
  The Delay Tolerant Networking Working Group is specifying the protocols needed to implement the Solar System Internetwork (SSI) concept. These protocols support the portion of the SIS communication domain where large delays, intermittent connectivity, and/or unidirectional communications links [大延迟、间歇性连接、单向通信链路] may be present. The main internetworking protocol in the Solar System Internet is the Bundle Protocol (BP) [捆绑协议?]. BP is a message-oriented store-and-forward communication protocol with optional reliability that is suitable for use when contemporaneous end-to-end connectivity cannot be guaranteed. BP routers may store data (bundles) before forwarding them, possibly for long periods of time. This allows routers to forward data even if the outbound communication link is not available when the data arrives. The Bundle Protocol and all the supporting protocols in the SSI suite are designed for these conditions. This is in contrast to many of the protocols in the Internet Protocol (IP) suite that at least implicitly assume low delays and end-to-end connectivity. The working group is specifying a profile of the Bundle Protocol as specified in Internet RFC5050 for use by CCSDS. BP has been demonstrated in a number of experiments both on the ground and with spacecraft, including the Deep-Space Networking Experiment (DINET), the Earth-Observing Mission-1 (EO-1) spacecraft, and various single- and multi-agency experiments on the International Space Station (ISS).
3. 声音（Voice）WG
4. CFDP修订（CFDP Revisions）WG：
  
  The objective of the WG is to introduce revisions to the CCSDS File Delivery Protocol (CFDP) that will enhance the protocol’s suitability for deployment in upcoming space flight missions. Among the proposed revisions are an increase in the limit on the size of file that may be transmitted, a mechanism for attaching metadata to each file data segment individually, and improved support for record structures in transmitted files.